1. Field of the Invention
The present invention relates to an electrical dust collector for an air cleaner being capable of cleaning the indoor air.
2. Description of the Prior Art
An ion-wind or ion-field type air cleaner disclosed in Japanese patent laid-open publication No. sho 61-61656 is known conventionally as an electrical dust collector for an air cleaner. As shown in FIG. 1, this ion-wind type air cleaner comprises a plurality of ionizing electrodes 1, opposing dust collecting electrodes 2 and accelerating electrodes 3. An ion-field is produced between the ionizing electrodes 1 and the opposing dust collecting electrodes 2 and dust is collected between the dust collecting electrodes 2 and the accelerating electrodes 3. A, plurality of auxiliary electrodes 4 are disposed between a plurality of the ionizing electrodes 1 and a plurality of the opposing dust collecting electrodes 2, respectively. The auxiliary electrodes 4 are supplied with a voltage whose potential is less than the voltage supplied between the ionizing electrodes 1 and the dust collecting electrodes 2.
With the air cleaner constructed as described above, there is an advantage that the air cleaner can generate an intensive ion-field but there are problems in that the structure is complicated and the manufacturing cost is high.
Also, an electrostatic precipitator as shown in FIG. 2 and disclosed in U.S. Pat. No. 3,740,927, which comprises a first section 10 having a plurality of negatively charged vertical wires w arranged between at least one or more pairs of positively charged vertical plates P1-P3. A second section 20 has a plurality of metallic grids G21 to G26 attached to the respective vertical plates P1-P3. A corona discharge may be developed between the positively charged plates and the negatively charged wires. The metallic grids are placed against the end of the first section 10 and are parallel to each other. The first and last grids G21 and G26 are connected a source of voltage so as to prevent corona discharge, and the remaining grids G22 to G25 are floated between the grids 21 and 26 so as to become charged by voltage induced in such grids 21, 26.
With this structure, particles of matter entering the second section 20 and traversing the opening of various grids will respond to the electric field between adjacent grids and to the aerodynamic flow pattern developed between all of the grids. As a result, there is an advantage that dust may be collected and removed from fluid medium, but there are problems in that the electrostatic precipitator is complicated and the manufacturing cost is expensive, and that since the metallic grids are in a floating state the dust collecting efficiency is decreased.
Another electrical dust collector for an air cleaner is shown in FIGS. 3(a) and (b), and will be now described simply.
Referring to FIGS. 3(a) and (b), in the structure of the electrical dust collector, an accelerating unit 22 is disposed centrally within a dust collecting unit 21, and sharp teeth 23, similar to saw teeth, act as the ionizing unit for charging dust particles P. The teeth are formed in a predetermined portion of the accelerating unit 22. With this structure, if the d.c. power 24 is supplied, dust particles P in the air D introduced in the dust collector are charged by the teeth 23 and then collected on the dust collecting unit 21.
In this case, however, since dust particles P to be collected are collected non-uniformly over the surfaces of the dust collecting unit 21, a spark phenomenon will occur. In addition, when the d.c. power supply 24 is a high voltage, a flame discharge is caused between the sharp teeth 23 formed in the accelerating unit 22 and the dust collecting unit 21, and a great deal of harmful ozone will be produced. Further, the ionization is performed concentratedly only on the sharp teeth formed in the accelerating unit 22, causing a problem in that the collecting efficiency of the dust collecting unit 21 is decreased.